West Asia: Land against Sea
One common theme in the history of West Asia has been the conflict between land-oriented people and sea-oriented people. Often there is a group of people living in West Asia who are mostly land-oriented. These people don't sail boats much, and they think of their kingdom as covering a certain piece of land. They often think that their land should include everything between the mountains of Afghanistan and the Mediterranean Sea. Some people who have thought this way are the Assyrians, the Persians, the Seleucids, the Parthians, the Sassanids, and the Umayyads.
But at the same time there is often a group of people living in West Asia who are mostly sea-oriented. These people sail boats a lot, and they think of their kingdom as being all the land around a certain body of water. These people often think that their land should include everything around the Mediterranean Sea. Some people who have thought this way include the Egyptians, the Greeks, the Romans, the Byzantines, the Crusaders, and the Ottomans.
But it is impossible to make both groups of people happy at the same time. They are always fighting over the strip of land which is in West Asia, but borders on the Mediterranean Sea (modern Turkey, Lebanon, Syria, and Israel). Even today, these are countries where there is a lot of fighting. So the Egyptians fought the Assyrians, the Greeks and the Egyptians fought the Persians, the Egyptians fought the Seleucids, the Romans fought the Parthians and the Sassanids, the Islamic Umayyads fought the Byzantines, and the Seljuks fought the Crusaders.

